# branch and loop




def if1():
    if 3 > 5:
        print("我在里面～")
        print("我也在里面～")
    print("我在外面～")


def if2():
    if 3 < 5:
        print("我在里面～")
        print("我也在里面～")
    else:
        print("我在外面～")




def if3():
    i = int(input("输入一个数字："))
    if i == 5:
        print("输入5")
        return
    elif i == 6:
        print("输入6")
        return
    else:
        print("输入的不是5跟6")


def if4():
    score = input("请输入得分：")
    score = int(score)
    if 0 <= score < 60:
        print("D")
    if 60 <= score < 80:
        print("C")
    if 80 < score <= 90:
        print("B")
    if 90 < score <= 100:
        print("S")


def if5():
    score = input("请输入得分：")
    score = int(score)
    if 0 <= score < 60:
        print("D")
    elif 60 <= score < 80:
        print("C")
    elif 80 < score <= 90:
        print("B")
    elif 90 < score <= 100:
        print("S")

def if6():
    score = input("请输入得分：")
    score = int(score)
    if 0 <= score < 60:
        print("D")
    elif 60 <= score < 80:
        print("C")
    elif 80 < score <= 90:
        print("B")
    elif 90 < score <= 100:
        print("S")
    else:
        print("请输入 0 ～ 100")





if __name__ == "__main__":
    if6()